Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, but it is puzzling for those who have it and for the doctors who treat it. IBS is a syndrome, a collection of symptoms with similar features that occur together in a pattern that your doctor can recognise. In typical cases, there is rarely any doubt about the diagnosis, although you may have symptoms in any part of your gastrointestinal tract, which stretches from the oesophagus (gullet) to the rectum. The term irritable is used to describe the reaction of the muscles in the intestine, which respond to stress by abnormal contractions. These may result in various combinations of the three main symptoms: pain, diarrhoea and constipation. In the UK, around eight million people have IBS. On average, each of them has 17 days off work a year, at an annual cost to the country of L500 million. Symptoms of IBS are equally common in men and women but women consult their doctors about these symptoms more often than men.